Method of and apparatus for burning pulverized fuel



Feb. 17. .1925.

C. F. MILLER METHOD OF AND APPARATUS FOR BURNING PULVERIZED FUEL Filed Sept. 16, 1921 2 Shgef0s-$heet 1 Feb. 17. 1925. 1,526,756

C. F. MILLER METHOD OF AND APPARATUS FOR BURNING PULVEBIZED FUEL Filed Sept. 16, 1921 v 2 Sheets-Sheet 2 Patented Feb. 17, 1925.

UNITED STATES PAT am OFFICE.

ormnrrs r. MIILEB, or MOORE, rmmsynvam, assrenon 'ro wmrmonousn anaemic & mnnurnc'runme conrm, a oonroaa'rron or rmmsrnvama.

7 METHOD or AND APPARATUS non. BURNING PULVER-IZED rm Appllcation filed September To all whom it mayconcem: v

Be it known that I, CHARLES F. Mmam, a citizen of the United States, and a resident of Moore, ,in the county of Delaware and State of Pennsylvania, have invented a. new and usefuljlmprovement in Methods of and Apparatus for Burning Pulverized Fuel, of

which the following is a specification;

My invention relates to a furnace for burning powdered fueland it has for an object the provision of an improved method and apparatus of the character designated m which the solid ash-dust particles shall be to a large extent separated withm the fire box from the gaseous products of combustion 1n order that a minimum amount of ash-dust shall be carried from the fire box with the products of combustion and shall find lodgment upon the tubes of the boiler, 1n the draft flues or stack leading therefrom, or shall be discharged from the stackinto the atmosphere. Y Q i In the accompanying drawings, Fig, 1 is a 'longitudinalview, partially in section 2 and partially in elevation, of a conventional water tube boiler equipped with my improved pulverized-fuel burning furnace; Fig. 2 is a fragmentary transversesectional view of the furnace illustrated in Fig. 1;

and Figs. 3, 4, and 5, are fragmentary longitudinal sectional views of modified constructionsof the pulverized-fuel burning furnace illustrated in Fig. 1. l

In steam generator installations equipped 5 with pull" ed-fuel burnin lierctofor nstructed, consi erable difliculty has be xperienced in'securing an efficient rate fheat transfer from the combustiongases to the boiler heating surfaces be- 40' cause of the high percentage of ash-dust which is carried alon with the combustion products into, the boiler and which settles uponthe'boiler heating surfaces formin a heat insulating coating thereupon. Furt' er is difiiculties in such furnaces have arisen because of the large quantities of'ash-dust settling inthe flue connections and in the chim-' "ney=which must beremoved therefrom at freent 'interval's, thus increasing the expense gg'operation of the steam generator and decreasing the efliciency of its operation during such "eriods because of the inrush of air into t e draft passages-and stack. Furtherfurnaces as a clean-out closure 14 16, 1921. Serial mi. 501,011;

slag-coated surfaces, in order to cause the fine troublesome particles of ash-dust to adhere to and become fused in the molten slag surfaces.

In carrying out my invention I introduce the mixed fuel and'air for combustion into the fire box of the furnace in theform of a thin sheet, substantially horizontal or tangential to the slag surfaces, thereby causing the whole molten slag surface to be covered with a thin film of flame, insuring a greater surface contact between'the flame andthe slag surface and a more complete separation of the dust particles from the gaseous products of combustion. Moreover this methodof combustion in which the flame impinges against the slag-coated surfaces serves in a large measure to protect the brick work of the furnace jfire box from the erosion comfiameupon the fire box wall.

tailed understanding of an apparatus, I indicate in Figure -1 a boiler plant in which the numeral 10 designates generally the boiler construction, which may be of any well-known type, the present invention beingin no wise limited to a use with any specific design of boiler. Located beneath the front end of the boiler is the fire box 11 which may be constructed of refractory material, as is the usual practice in furnace construction. Beneath the rear end of the boiler is the usual settlingchamber 12. A slag refuse chamber 13 having the usual and communicating thcrethrough with a suitable pit 15 is disposed beneath the 'fire box in suchmanner as to receive ash and slag from the fire box. The fire box 11 comprises a front wall 16,

' monly caused by the impingement of the Referringfto'the drawing for a more deside walls 17 a rear bridge wall 18 and a bottom wall 19, the latter having its upper exposed surface lying in a plane slightly inclined to the horizontal and having an upwardly extending dam 20' at its rear end,

i the top of the dam being substantially at the cross section at their outer extremities and I are flattened and downwardly declined toward the inner extremities, the arrangement being such that the several nozzles deliver into the furnace a thin sheet of mixed pulverized fuel and air at a slight inclination to the horizontal. Each'of the several nozzles is suitably connected by. a nipple 22 with a manifold 23 which receives themixed pulverized fuel and air through a conduit 24 leading from a conventional mechanism 25 for phlverizing the fuel andmixing the pulverized fuel with air. The constructional characteristics of the mechanism 25 form no part of my present invention and hence a detailed description thereof is deemed unnecessary in the present application.

The inclined upper surface of the bottom wall 19 cooperates with the dam 20 atthe rear end thereof to form a shallow basin 26- which 1 preferably fill with a fusible slag. The top and rear walls of the dam 20 and at least a lower -.portion 27 of the bridge wall 18 are also preferably coated with slag to protect the Walls from the erosive action of the flame and to catch the dust particles as is hereinafter more fully described. One or more: vertically disposed openings 28' exlendingfrom thefire box 11 at the rear of the dam 20 and opening into the slag pit 13 are provided for the withdrawal of excess slag and ash from the fire box.

The manner in which my improved pulverized-fuel burning furnace operates is clear from the above description. In-brief, the commingled pulverized fuel and air is delivered at a considerable pressure through the conduit 24 to the manifold 23; thence distributed to the several nozzles 21 from which the mixed fueland air is discharged into the fire box 11 in a thin sheet horizontal with respect to the front wall of the furnace. Combustion ensues upon the admission of the mixed fuel and air into the furnace and the resulting thin sheet of flame is directed so as to impinge at a slight angle against the surface of the molten slag within the basin formed by the dam 20. The flame plays over substantiallythe enlire surface of the slag, which is consequently maintained in a molten condition, so that the solid dust particles readily adhere to and become fused in the heated slag and any unburned particles caught in the molten slag are maintained at a high temperature until they have been completely consumed. The flame slides along the surface of the molten slag and impinges against the bridge wall 18 against which the flame spreads and eddies, causing dust particles still held in suspension in the flame to adhere to and become fused with the slag coating on the bridge wall '18.

It is evident that this direct and intimate contact of the flame with the slag-coated surfaces which is successively repeated by bringingthe flame into the direct intimate contact with other slag-coated surfaces serves to effect the separation of a large percentage of the ash-dust from the combustion gases before these gases are delivcred through the upper portion of the fire box 11 to contact with the heating surfaces of the boiler 10.

The construction disclosed in Fig. 3 is similar to that illustrated in Figure 1. The relation of the walls 16, 17, 18 of the fire box are identical with that disclosed in Figure 1. The bottom wall 30 however, is constructed to afford a greater slag-coated surface subjected to cddving currents of the thin sheet of flame. s shown, the bottom wall 30 is provided with an inclined upper surface 31 adjacent the front of the furnace, an intermediately disposed dam 32, and an inclinedsurfaoe 33 at the rear of the dam 32 at a considerably lower level than the surface 31. This construction serves to provide a shallow pool 34 which-is filled with slag and against which the flame discharged from the nozzles 21 impinges. In addition, the flame is caused to spread and eddy against the slag-coated surface 35 on the lower portion of the bridge wall 18, the

slag-coated surface of the rear wall of the dam 32, and the inclined surface 33. The operation of the furnace above described is in every respect similar to that recited in relation to the furnace illustrated in Figure 1, the construction differing only in that the slag-coated surface against which the flame from the nozzles directly impinges is decreased in extent and the slag-coated surface against which the fiame is brought into eddying contact is increased in extent.

The construction illustrated in Figure l differs from the constructions heretofore described in that the slag-coatcd surfaces to which the eddying portion of the flame are brought into contact are arranged at a higher level than the slag-coated surfaces against which the flame directly impinges and in a stepped relation thereto in such manner that the excess slag flows downwardly over the stepped surfaces as to be discharged at the front of the furnace into the slag pit. As shown, the front'and side walls 16 and i 1i of the fire box and the nozzles 21 in the front wall thereof, are in all respects identical with the construction described in con nection with Figure 1. The bottom wall 40 of the fire box comprises a horizontally disposed portion 41 which is spaced at oneor more points from the front wall 16 to form the slag discharge openings 42. The rear portion of the bottom wall .40 comprises a series of sinuate steps rising from the upper -surface ofthe front portion 41 and extending intothe bridge wall 18. Rising from the top of the series of steps 42 a portion 43 of the bridge 18 overhangs the steps 42, which portion 42 may also present a plurality of Vertically stepped surfaces against which the flame may eddy. In operation, the thin sheet of flame from the nozzles 21 impinges at a slight angle upon the molten slag on the bottom wall portion 41 and is deflected upwardly into eddying contact w' h the slag-coated surfaces upon the series of steps 42 and upon the overhanging portion 43 of the bridge wall 18. The dust particles adhere to the slag and the excess slag,

collecting upon the walls of the fire box flows downwardly and forwardly across the portion 41 of the bottom wall through the wall to form a shallow basin 53 for containing molten slag. The rear portion .of the bottom wall 50 comprises a series of sinuate steps 54 at the rear of whi h are one or more openings 55 leading into'the slag pit 13. The bridge wall 18- is constructed to overhan the rear portion of the fire box, the over anging portion being preferably serrated as shown at 56, as in the, construction illustrated in Figure 4 heretofore described. The bottom wall 50 and at least the lower portion of the bridge wall 18, including the serrated overhanging portion 56, are coated with a'suitable slag. The sheet of flame issuing from the nozzles 21 first im inges against the slag in the shallow basin 53 to which some ofthe solid ash particles adhere and is deflected in a substantially horizontal flame toward the rear of the firebox. The descending step portion 54 of the bottom wall induces downwardly eddying currents of the burning gases which intimately contact with the slag-coated surface of the step portion 54.

flame and the overhanging portions to deflect "the upwardly eddyin'g combustion products so as to further remove theash particles therefrom. 1

It is evident. from the above description that the essence of my invention resides in the introduction into the fire box of a furnace of a thinsheet of mixed powdered fuel and air in such manner as to produce a resulting thin sheet of flame, in bringing the flame into direct and intimate contact with a surface of molten slag, and in causing the flame deflected from the slag surface to spread and eddy againfi other slag-coated surfaces so as to remove the ash-dust particles from the gaseous products of com-- bust-ion. The invention is then essentiallya method of and apparatusfor. burningpowdered fueljand separating'the solid from the gaseous products of combustion, and obviously may be carried out within furnaces of varied construction.

While I have shown my invention in several forms, it will be obvious to those skilled in the art that it iis not so limited, but is susceptible of various other changes and modifications witllout departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed there'- upon as are imposed by the prior art or as claims. 1

What I claim is: l h 1. The method of bur comminuted fuel which comprises forcefu y discharging a .thin sheet of intimately mixed comminuted, fuel and air into a; furnace in a substantially horizontal plane, causing a are specifically setforth in the appendedv combustion of the mixed fuel and air upon their ientry into the furnace, and directing the resulting thin film of flame along the horizontally disposed surface of a'layer of" molten slag. 1

2. The method of burning comminuted fuel which comprises forcefully discharging a thin sheet of intimately mixed com- The bridge wall 18 serves to spread the 7 minuted fuel and air into a furnace'in a plane slightly inclined to the horizontal,

causing a combustion of the mixed fuel and air upon their entry into the furnace, and

directing the resulting thin film of, flame,

along the horizontally disposed surface of a layer of molten slag.

3. The method of burning comminuted fuel which comprises forcefully discharging a thin sheet of intimately mixed comminuted fuel and air into a furnace in a substantially horizontal lane, causing a combustion of the mixed uel and air upon their entry into the furnace, directing the resulting thin film of flame along the hori .zontally disposed surface of a layer of molten slag and then causing the horizontally projected flame to change its direction Y of travel whereby upon the change of direction of the flame solid products of combustion are separated from the combustion gases.

4. The method of burning comminuted fuel which comprises forcefully discharging a thin sheet of intimately mixed comminuted fuel and air into a furnace in a substantially horizontal plane, causing a combustion of the mixed .fuel and air upon their entry into the furnace, maintaining- .a temperature within the furnace sufficient to fuse ,the solid products of combustion, and directing the thin film of flame along the horizontally disposed surface of a body of molten slag formed by the accretion of fused products of combustion.

, 5. In the art of burning comminuted fuel in a furnace provided with a substantially plane surface upon'which a layer of molten slag may slowly flow to a slag pit, the method which comprises forcefully discharging a thin sheet of intimately mixed comminuted fuel and air into thefurnace and air to effect upon combustion aforwardly moving thin film of flame, said fire box: *having a wall membef' covered with slag the surface of which is so disposed as to lie approximately in the plane in which the sheeet of flame is projected, whereby i the thin film of flame engages and sweeps along the slagged surface.

i .7. In combination in a furnace for burning comminuted fuel, a fire box having a wall upon which the fused products of combustion collect in the form of molten slag,

means "for forcefully injecting into the fire box a thin sheet of intimately mixed comminuted fuel and air in such manner as to effect upon combustion a forwardly III'OV-' ing thin film of flame, said injecting means and said wall being so dis osed relatively one to the other that the lm of flame is prr'ijected along the slagged surface of the "21 8. In combination in a furnace-for burning comminuted fuel, a fire box having a wall upon which the fused products of combustion collect in the form of molten slag, means for forcefully injecting into the fire box a thin sheet of intimately mixed comminuted fuel and air in such manner as to effect upon combustion a substantially recthe resulting thin film of tilinearly m'ovin film of flame, said wall being so dispose that its slagged surface is contiguousto the rectilinear path of travel of the flame and is thereby enveloped by the flame.

9. In combination in a furnace for burn-- ing comminuted fuel, a fire box having a wall upon which the fused products of combustion collect in the form of molten slag,

means for forcefully injecting into the fire otherthat the forwardly moving film of flame impinges upon the slagged surface at such small angles as to cause the flame to travel in contact with the slagged surface of said wall with substantially no deflect-ion therefrom during the early stages of combustion.

. 1,0. In combination in afurnace for burning comminuted fuel, a fire'box having a wall upon which the fused products of combustion collect in the form of molten slag, means for forcefully injecting into the fire box a thin sheet of intimately mixed com-. minuted fuel and air in such manner as to effect uponcombustion a forwardly moving thin film of flame, said injecting means and said wall being so disposed relatively to each other that the forwardly moving film of flame impinges upon the slagged surface at such small angles as to cause the flame to travel in contact with the slagged surface of said wall with substantially no deflection therefrom during the early stages of combustion, and a second furnace wall so disposed with respect to the forwardly moving film of flame as to cause a marked change in the direction of the travel of the flame whereby the solid )roducts of combustion are largely separated from the gaseous products of combustion.

11. In combination in a furnace for burning comminuted fuel, a fire boxhaving a wall upon which the fused products .of combustion collect and present a substantially horizontally exposed surface of molten slag, means for forcefully injecting into the fire box a thin sheet of intimately mixed comminuted fuel and air in such manner as 'to effect upon combustion a forwardly moving thin film of flame, said injecting means being so disposed with respect to the wall that the forwardly moving film of flame envelops the exposed surface of slag with sub stantially no deflection therefrom.

12. In combination in a furnace for burnin; comminuted fuel, a fire box having a wall u pon which the fused products of combustion collect and present a substantially horizontallyegrlposed surface of molten slag, horizontally igned nozzles in the front wall of the fire box for forcefully injecting into thefire box a thin sheet ofintimately mixed comminuted fuel and air .and so disposed that a substantial] horizontal film of flame travels along an envelopstheex posed slag surface. 13. In combination in a furnace forburning comminutedfuel a fire box having a bustion collect and present a substantially horizontally exposed surface ,of molten slag, means for forcefully injecting into the fire box a thin sheet of intimatelymixed comminuted fuel and air in such manner as to effect upon combustion a forwardly moving thin film of flame, said injecting means bein so disposed with respect to the wall that the forwardly moving film of flame envelops the exposed surface of slag with substantially no deflection therefrom, and means for abruptlydeflecting said sheet of flame after its assage beyond said horizontal slagged 1 S111 ace.

14;. In combination in a furnace fon burning comminuted. fuel, a fire box having a wall upon which the fused products ofcom the forwardly movingfilm of flame envelops the exposed surface .of slag with substantially no deflection therefrom, and wall means for reversing the direction of travel of said fl'ame after its passage beyond said horizontal sla 'ged surface. wall upon which the fused products of com- 1-5. In combination in a furnace for burning comminuted fuel a fire .box having a wall upon which the fused products of com bustion collect and ,present a substantially horizontally exposed surface of molten slug,

means for forcefully injecting into the fire box a thin sheet of intimately mixed comminuted fuel and air in such manner asto effect upon combustion .a forwardly moving thin film of flame, said injecting means being so disposed with respect to t e wall that the forwardly moving film of flame envelops the exposed surface of slag with. substantially no deflection therefrom; means for abruptly deflecting said sheet of flame after its passage beyond said horizontal slaggedsurface, and a means for withdrawingthe solidand fused products of combustion provided between said slagged surface and said deflecting means.

In testimony whereofQI have hereunto.v subscribed my name this 17th day of August, 1921. MILLER. 

